1. Field of the Invention
The present invention relates to a method for determining the plausibility of objects in driver assistance systems of motor vehicles which have a locating system, e.g., a radar system, for locating objects in the surroundings of the vehicle and for measuring lateral offsets of these objects in the direction perpendicular to the direction of travel, in which method a travel route envelope is defined for the host vehicle, and the plausibility of moving objects is determined according to whether they are inside or outside of the travel route envelope.
2. Description of Related Art
In driver assistance systems which support the driver in guiding a motor vehicle, it is often necessary to determine the plausibility of located objects, particularly other preceding vehicles. By this is meant that it is necessary to decide whether or not these objects must potentially be taken into account in the execution of the assistance function in question. Examples for driver assistance systems in which this problem occurs are, for instance, adaptive vehicle speed controllers, also known as ACC systems (adaptive cruise control), in which the traveling speed of the host vehicle is adjusted in such a way that a located preceding vehicle is followed at a suitable distance, or warning and safety systems which are intended to warn the driver of an imminent collision and/or to initiate automatic measures for mitigating the effects of a collision.
To determine object plausibility in such systems, a travel route envelope of suitable width is defined which describes the anticipated course of the host vehicle, and objects that are within this travel route envelope are checked for plausibility in an ACC system in the sense that they are graded as potentially relevant obstacles to which the vehicle speed controller may have to react. Among the objects whose plausibility has thus been determined, one object, typically that having the smallest distance to the host vehicle, is then selected as the target object for the distance control.
In general, the width of the travel route envelope should correspond approximately to the width of the traffic lane being used by the host vehicle. However, the following conflict of aims occurs when exactly defining this width. On one hand, the width should be selected to be as great as possible, so that potential target objects can be detected early on, especially when the course of the roadway is not straight, and therefore the speed can be adjusted in plenty of time. On the other hand, if the travel route envelope is so wide that it extends to parts of adjacent lanes, there is the danger that so-called adjacent-lane disturbances will occur, that is, that the plausibility of objects which are in the adjacent lane and therefore are not actually relevant will be falsely determined, and these objects will be included in the evaluation, so that faulty reactions occur in the system.
To optimize the width of the travel route envelope, it has already been proposed to enlarge the travel route envelope beyond a certain basic width as soon as a target object has been detected, so that this target object can then be followed in a steadier manner. However, this has the disadvantage that the front vehicle being followed is retained as the target object unnecessarily long, even when this vehicle changes to an adjacent lane, and the adjacent-lane disturbances occurring have a longer and therefore substantially more intense effect.
Another approach is to differentiate between various types of roads, namely, freeways on one hand and country roads on the other hand, based on data provided by a navigation system or based on locating data supplied by the locating system. On freeways, which generally have several traffic lanes per travel direction, a narrower travel route envelope is then selected in order to avoid adjacent-lane disturbances, while on country roads, which generally have only one traffic lane in each direction, a wider travel route envelope is selected, thereby permitting earlier detection and steadier tracking of the target object. Here, however, there is the disadvantage that on freeways, the target object can only be detected relatively late, and thus the approach behavior of the host vehicle is impaired. On the other hand, on country roads, particularly on well-enlarged, very broad country roads, as well as in the case of crawler lanes, acceleration lanes or turn-off lanes occasionally present on country roads as well, there is a high susceptibility for adjacent-lane disturbances.